Final Comment Period for library stabilizations in 1.4

Hello everyone! Now that 1.2 has been released it's time to start focusing on what's going to be stabilized for 1.4. The library subteam has decided to try a bit of a new strategy for this cycle. We've just recently finished creating tracking issues for all unstable features in the standard library, and we're going to use these issues to track what's going to be stabilized for 1.4.

To that end, I've just gone through and tagged a number of issues with final-comment-period. Each of these issues represent features that will be either stabilized or deprecated in the week before the 1.4 beta is cut. If you're using any of these features and would like to see changes, please comment on the associated issue! If any changes are made the FCP will end for that issue and it will become a candidate for 1.5 instead.

Pending final comments during this period, the features will all be stabilized or deprecated in one go (we won't post incremental PRs in the middle). For reference, here's a list of all features that have moved into final comment period:

APIs to Stabilize

APIs to Deprecate